Bojan Ogorelec

The role of sedimentary biogeochemistry in the formation of hypoxia in shallow coastal waters (Gulf of Trieste, northern Adriatic)

Abstract Pore water measurements of dissolved organic matter (DOM) and inorganic nutrients in the surficial sediment of the Gulf of Trieste showed the highest concentrations to be in late summer due to the higher microbial activity and restricted upward fluxes to the overlying water because of density stratification in the water column. The benthic fluxes of DOM, in terms of dissolved organic carbon (DOC), nitrogen (DON) and phosphorus (DOP), and the inorganic nutrients NH+4 and PO3−4, measured in parallel with sediment oxygen consumption (SOC) and production, showed in general a net influx indicating benthic consumption. Only strong DOC fluxes out of the sediment prevail in late summer. The bulk of DOC in pore water was found to be refractory, with a significant proportion consisting of a high molecular weight fraction. DON and DOP were more reactive in aerobic and anaerobic pathways of decomposition and not directly temperature dependent, probably because of a randomly fluctuating supply of degradable sedimentary organic matter and oxidants. In constructing the mass balance of C, N, and P it emerged that the sediment is primarily anoxic because the SOC is higher than benthic oxygen production. Oxygen must be therefore introducted to the sediment-water interface by physical factors and water column photosynthesis to prevent bottom layer hypoxia and anoxia in the period of strong density stratification in the water column. The role of particulate organic matter (POM) sedimentation is not of primary importance to SOC, and a fraction of summer POM is probably refractory and of allochtonous origin.

Microfacies and diagenesis of lower and middle cretaceous carbonate rocks of NW-Yugoslavia (Slovenia, Trnovo area)

SummaryA profile of about 1400 m thickness near the village of Trnovo in the Trnovo forest in SW-Slovenia was studied for the microfacies and diagenetic development of the carbonate rocks. Because of the detailed biostratigraphic subdivision being just in improvement, the interval from the problematic Jurassic/Cretaceous to the Tertiary boundary (Berriasian-Cenomanian, fault, Senonian) was subdivided into ten zones and several subzones. These subdivisions are of practical use and can be found in profiles studied in other areas of SW-Slovenia and Istria as well. The data are based on field observations, thin sections and acetate peels.The following development can be recognized: (1) During the Berriasian(?)-Hauterivian a shallow-marine to intertidal restricted environment was established on the coherent Dinaric Carbonate Platform. This is indicated by low faunal diversity and numbers as well as the common occurrence of marine and meteoric vadose cements, birdseyes and algal-layers.Clypeina jurassica, Bankia striata, Favreina salevensis, and trocholinid foraminifera are chacteristic of the lowermost part (Uppermost Jurassic?, Berriasian-Valanginian) of this section. (2) In the Barremian-Aptian a lagoonal environment with patch reefs was established, characterized by normal marine conditions. High faunal and floral diversity and large numbers occur (hydrozoans, corals,Palorbitolina lenticularis, Salpingoporella dinarica). During this time period the platform was divided into smaller tectonic units with different facies development. (3) An open marine ingression from the Slovenian Basin occurred in the Albian, indicated by dolomitic limestones rich in sponge spicules and silica nodules and layers. (4) In the Cenomanian, mainly bioclastic sands (rich inOrbitolina conica) and micritic limestones (withPithonella) were deposited in alternation with micrites rich in ostracods and limestones containing birdseyes, vugs, and microsparite. This indicates a strong interfingering of different facies on a gently dipping ramp, probably due to sea level fluctuations. (5) The Turonian is missing in the section analyzed due to a fault. (6) In the Senonian bioclastic sands rich in fragments ofSabinia sp. were deposited around rudist mud mounds formed in inner shelf areas under normal marine conditions. Eocene flysch overlies the sequence and influences it diagenetically by silica authigenesis in the upper decimeters of the underlying limestones.ZusammenfassungIm SW-Slowenien wurden die Mikrofazies und Diagenese eines ca 1400 m mächtigen Kreide-Profils (Berrias-Senon) nahe der Ortschaft Trnovo im Ternowaner Wald untersucht. Die detaillierte biostratigraphische Untergliederung wird zur Zeit von slowenischen Kollegen durchgeführt. Aus praktischen Gründen wird daher in der vorliegenden Arbeit die Untergliederung des Intervalls in zehn Zonen und mehrere Subzonen vorgenommen, die auch in anderen in SW-Slowenien und in Istrien untersuchten Profilen nachgewiesen werden können. Die vorliegenden Daten wurden aus Geländebeobachtungen, Dünnschliffen und Folienabzügen abgeleitet. Folgende Entwicklung ist zu erkennen. (1) Während des Barrias (?)-Hauterive herrschte ein flachmarines bis intertidales Environment auf der Dinarischen Karbonatplattform. Die geringdiverse Fauna und wenige Individuen belegen dies ebenso wie marin- und meteorisch-vadose Zemente sowie Fenstergefüge und Algen-Lagen.Clypeina jurassica, Bankia striata, Favreina salevensis und trocholinide Foraminiferen sind charakteristisch für den untersten Teil dieser Folge (Oberstes Tithon?, Berrias-Valendis). (2) Im Barreme-Apt bildete sich unter normal marinen Bedingungen ein lagunäres Milieu mit Patch-Riffen aus. Große Faunen- und Florendiversität und Individuenzahlen werden gefunden (Hydrozoen, Korallen,Palorbitolina lenticularis, Salpingoporella dinarica, Milioliden). In dieser Zeit zerbrach die Dinarische Karbonatplattform in kleinere tektonische Einheiten, auf denen unterschiedliche Faziesentwikklungen stattfanden. (3) Während des Alb wurden zeitweise schwach dolomitische Kalke mit zahlreichen Schwammnadeln und Kieselknollen und Hornsteinlagen gebildet, die eine offen marine Ingression vom Slowenischen Trog her belegen. (4) Im Cenoman wurden subtidale bioklastische Sande (häufigOrbitolina conica) und mikritische Kalke (mit Pithonellen) in Wechsellagerung mit Ostrakoden-Biomikriten und Kalken mit Fenstergefügen, vugs und Mikrosparit gefunden. Daraus ergibt sich eine durch Meeresspiegelschwankungen bedingte starke Faziesverzahnung auf einer schwach geneigten Rampe. (5) Das Turon fällt an einer Störung aus. (6) Im Senon treten bioklastische Sande mit zahlreichen Bruchstücken vonSabinia sp. auf. Sie wurden nahe bei Rudisten-mudmounds auf dem Innenschelf unter normal marinen Bedingungen abgelagert. Die Folge ist von eozänem Flysch bedeckt, der die oberen Dezimeter der Kreide-Kalke mit Quarz-Authigenese diagenetisch beeinflußt.

Decastronema barattoloi (DE CASTRO), characteristic fossil of the Palaeocene and the Eocene peritidal sediments from the Adriatic carbonate platform

The renewed deposition in the Palaeogene and the oldest part of the non-interrupted Palaeocene succession is characterized by the presence of Decastronema barattoloi (DE CASTRO), cyanobacterial tubes originally described in the Apennines. The reinterpretation of limestones from several sections located in the Kras region (NW part of the AdCP: Basovizza, Dolenja vas, Sopada, ?ebulovica) confi rmed the presence of these microfossils in peritidal sediments of Danian age (SBZ 1). The Cuisian (Late Lower Eocene) sediments, from eastern Istria (Brnjci section), Cres Island (Koroma?na Cove section) and Ravni kotari (Benkovac–Korlat section) contain individuals of this species in great numbers. The cyanobacterial tubes are scattered in laminated, fi ne grained mudstones and wackestones, immediately above the Cretaceous sediments (occasionally above bauxites or breccias). The Decastronema-bearing sediments pass upward into the Foraminiferal limestones of Cuisian age (SBZ 11, based on conical agglutinated foraminifera and alveolinids), allowing the age determination of the cyanobacterial remnants. The Palaeocene specimens are minute (up to about 180 ?m long), thick walled tubes that occur with the index fossil Bangiana hanseni DROBNE. The Eocene forms accompanied by ostracods, pelecypods, and miliolid and rotaliid foraminifera are segmented tubes, up to 400 mm long and usually thin walled.

Identification of the Palaeocene–Eocene Boundary Based on Larger Foraminifers in Deposits of the Palaeogene Adriatic Carbonate Platform, Southwestern Slovenia

Two sections located in the northwestern part of the Palaeogene Adriatic carbonate platform (PgAdCP) were measured and sampled to document the complexity of changes at the Palaeocene–Eocene boundary. Carbon and oxygen isotope records in combination with a detailed study of larger benthic foraminifera (LBF) are used to describe the turnover of foraminifera and to refine the shallow benthic zonation scheme.

Microbialites as Markers of Biotic and Abiotic Events in the Karst District, Slovenia and Italy

Microbialite units are commonly found within the Mesozoic–Tertiary carbonate succession of the Karst District of Slovenia and Italy. They record environmental conditions, which are linked with both local and global events.

Rudists and Larger Foraminifera below the Cretaceous-Tertiary Boundary in the Dolenja Vas Section

The Vreme beds are part of the Liburnian Formation. At Dolenja vas which is situated on the Trieste-Komen platform, the Upper Maastrichtian age has been proved with co-occurring rudistids and foraminifera.

Borehole MET-1/04 near Metlika, between the External and Internal Dinarides (SE Slovenia)

Raziskovalno-kaptažna vrtina MET-1/04 pri Božakovem, vzhodno od Metlike v Beli Krajini, je globoka 841 m. Namen vrtanja je bil zajeti geotermalno vodo, ki bi bila uporabljena v turisticne namene. Obmocje vrtine leži na prehodu zunajnih Dinaridov, ki so v splosnem zgrajeni iz mezozojskih plitvomorskih karbonatnih kamnin, v Notarnje Dinaride. Za slednje so znacilne predvsem globljemorske klasticne kamnine, ravno tako mezozojske starosti. Strukturna znacilnost obmocja je niz dinarsko usmerjenih narivov, ob katerih so Notarnji Dinaridi narinjeni na Zunanje. Sama vrtina je locirana v zgornjekredni flisni skladovnici, ki je odložena transgresijsko na zgornjejurske apnence. Flisno skladovnico do globine 182, 5 m sastevljajo breca, konglomerat ter kalkarenit in lapor. Navzdol do globine 275 m sledijo spodnjekredni apnenci, ki pripadajo ali velikim olistolitnim blokom v bazi flisa ali pa tektonskemu bloku v narivni luski. Do dna vrtine na 841 m nastopaju grebenski apneci zgornjejurske starosti. Zgornji del apnecev pripada zgornjemu malmu, spodnji del pa je mogoce že spodnjemalmske starosti. V vrtini sta bili ugotovljeni dve vodonosni coni in sicer v intervalu od 92.5 do 184 m ter v intervalu od 220 do 355 m.